In 2004, Jobs underwent a complicated but successful surgery to remove a tumor in his pancreas, and was back at work within a few months. While the procedure is highly successful for the form of pancreatic cancer that Jobs had, it also removes much of the pancreas and some of the digestive tract. This can lead to further complications, such as the dramatic and visible weight loss Jobs' suffered in 2008.

Jobs' last medical leave happened right before Apple's last Macworld attendance in 2009. This latest absence comes just as Apple is about to launch the iPhone on Verizon in the US and is expected to announce new products, including a new iPad, in the coming months.

During the previous two medical absences, Jobs left the day-to-day operations of Apple to COO Tim Cook. Since then, Cook has taken on more responsibilities that were once under Jobs' exclusive purview, and Cook is once again taking over while Jobs is away.

Here's the text of the e-mail Jobs sent to Apple's staff:

At my request, the board of directors has granted me a medical leave of absence so I can focus on my health. I will continue as CEO and be involved in major strategic decisions for the company.

I have asked Tim Cook to be responsible for all of Apple’s day to day operations. I have great confidence that Tim and the rest of the executive management team will do a terrific job executing the exciting plans we have in place for 2011.

I love Apple so much and hope to be back as soon as I can. In the meantime, my family and I would deeply appreciate respect for our privacy.

It's the mark of an elite CEO that the organization he built and staffed can continue to prosper and thrive during periods of absence and even after he's no longer with the company.

IME Tim Cook isn't as charismatic as Jobs (then again, who is?), but he is a perfectly competent presenter. And he has more than proven his ability to lead Apple both as a COO and in acting as CEO when Jobs is away. I agree that Schiller, Ive, et al have been doing a great job (though I could do without Forstall's lengthy parade of app demos!).

It's the mark of an elite CEO that the organization he built and staffed can continue to prosper and thrive during periods of absence and even after he's no longer with the company.

IME Tim Cook isn't as charismatic as Jobs (then again, who is?), but he is a perfectly competent presenter. And he has more than proven his ability to lead Apple both as a COO and in acting as CEO when Jobs is away. I agree that Schiller, Ive, et al have been doing a great job (though I could do without Forstall's lengthy parade of app demos!).

As someone said on the Ars facebook page... Al Gore. He'd make the perfect public face of Apple. Heh.

It's the mark of an elite CEO that the organization he built and staffed can continue to prosper and thrive during periods of absence and even after he's no longer with the company.

IME Tim Cook isn't as charismatic as Jobs (then again, who is?), but he is a perfectly competent presenter. And he has more than proven his ability to lead Apple both as a COO and in acting as CEO when Jobs is away. I agree that Schiller, Ive, et al have been doing a great job (though I could do without Forstall's lengthy parade of app demos!).

Weren't those same people at Apple before Jobs came back in the late 90's? I know some were if not all.

I guess it answers the question as too why the Murdoch announcement was postponed. Interesting how Apple managed to announce this on a Market holiday? Personally, I think Steve will be missed as a visionary and a marketing genius whenever he is unable to play the role of CEO of Apple. Tim Cook as I have heard him at the Verizon iPhone announcement is no Steve Jobs and really don't expect him to be. But what is Apple going to do when Steve can no longer perform his magic? Much to what has happened to Microsoft which never had a Steve Jobs salseman. Apple has to begin to realize a company without Steve.

I've never been a fan of Apple products and Steve Jobs but there's no denying the man is single-handedly responsible for revolutionizing the personal computer, portable media player, content distribution, mobile phone, and tablet computer markets. Jobs tactfully negotiated deals that would allow the beginnings of transformation in each one of those markets (okay, the early days of the personal computer may have been a little botched but he's had a pretty good track record since.)

While the devices I own may not be Apple-branded, they're all influenced very much by Steve Jobs as he forces his competitors to step-up their game and produce quality products. Would Android or WP7 exist, at least in its current form had it not been for Steve Jobs and the IPhone?

I hope he has a speedy recovery from whatever it is that ails him as the world of consumer electronics and technology would be a much less innovative place without him!

Weren't those same people at Apple before Jobs came back in the late 90's? I know some were if not all.

I still say 90% of apple's recent success is due to Jobs.

Absolutely not, all the current C-level staff was carefully brought together by Jobs in his, erm, "second coming".

Jobs is 100% responsible for creating the extremely successful Apple version 2. Wheter he's still crucial for this Apple's success, it's difficult to say.I'd say its ability to execute in the short and mid term should be completely not relying on Jobs anymore.Long term strategies, negotiating ability at the very top level, and that "sixth sense" for new products, who knows, we'll just need to sit and watch. I'd say that everything comes to an end eventually, even the infallibility of a top CEO instinct, so in the long term we would've had to sit and watch even if Jobs was in perfect health.

As someone said on the Ars facebook page... Al Gore. He'd make the perfect public face of Apple. Heh.

He would be a good leader, but I think his political background might be too polarizing. Apple is a progressive company, but Jobs is apolitical for the most part. Last I heard, Rush Limbaugh uses a Mac. Do you think he'd change to PCs (and make a huge deal about it) if "algore" is CEO?

We must face facts...he's not going to go on forever, and don't think he really want's to try.

So who can he trust to run the factory when he leaves and take care of the Phil Schiller's for him? Not a grown up. A grown up would want to do everything his own way, not Steve's. So that's why he decided a long time ago that he had to find a child. A very honest, loving child, to whom he could tell all his most precious computer making secrets. So he's going to send out five golden tickets...

It's the mark of an elite CEO that the organization he built and staffed can continue to prosper and thrive during periods of absence and even after he's no longer with the company.

IME Tim Cook isn't as charismatic as Jobs (then again, who is?), but he is a perfectly competent presenter. And he has more than proven his ability to lead Apple both as a COO and in acting as CEO when Jobs is away. I agree that Schiller, Ive, et al have been doing a great job (though I could do without Forstall's lengthy parade of app demos!).

Weren't those same people at Apple before Jobs came back in the late 90's? I know some were if not all.

Ive was "discovered" and hand-picked by Jobs, Cook joined in March 1998 (~2 years after Jobs came back and the yeah he started killing projects in drove, Cook is responsible for pulling Apple out of manufacturing and streamlining the supply chain), Schiller was indeed at Apple before Jobs went back, but it's Jobs who put him on the executive team (in 1997). Finally Forstall came from NeXT.

maybe it's just the board of directors who poisoned its coffee... so now Apple will be able to pursuit different, more mainstream and developer friendly projects.

Why on gods green earth would they do that? Apple is making more money than God right now.

Whatever Jobs has done, there's no denying that Apple has never had it this good ever before and to change course now...well, lets just say that most board member probably wouldnt have the guts to do so even if it was the better choice.

Hope he gets better. I hate to see people suffer especially from the likes of cancer.

What is troubling to me, when I was watching the news this morning, is that some "Money" news anchor comes on and talks about how they are going to lose money because of it. Damn the guys health, who cares. Is is going to cost me some money? /sarcasm

Weren't those same people at Apple before Jobs came back in the late 90's? I know some were if not all.

I still say 90% of apple's recent success is due to Jobs.

Absolutely not, all the current C-level staff was carefully brought together by Jobs in his, erm, "second coming".

Yeah, many of the guys worked for him at NeXT. Scott Forstall is ex-NeXT, as is Bertrand Serlet. Phil Schiller joined Apple soon after Apple bought NeXT, so he might have been hired by Jobs. One guy who was already at Apple when SJ came back was Johnny Ive. Cook was hired by Steve Jobs in 1998, Bob Mansfield joined Apple in 1999, Ron Johnson in 2000.

Yeah, many of the guys worked for him at NeXT. Scott Forstall is ex-NeXT, as is Bertrand Serlet. Phil Schiller joined Apple soon after Apple bought NeXT, so he might have been hired by Jobs. One guy who was already at Apple when SJ came back was Johnny Ive. Cook was hired by Steve Jobs in 1998, Bob Mansfield joined Apple in 1999, Ron Johnson in 2000.

Do we know if any that left Apple with Steve to form NeXT also made it all the way back to Apple when Steve came back?

I remember AAPL going down 50% once overnight - this might be the same here. Ok so Apple is going to continue to thrive, and everything will be OK in a few months when Jobs comes back. The risk is he doesn't come back. The stock is priced in expectations of growth and while Apple is going to kill with the iPad 2 and iPhone 5, and new Macs, without Jobs, they're going to lose momentum in 2012. How can they not. Jobs is Apple, basically.

On a personal note I wish Steve Jobs all the best, may he come back once again. He's done it twice already.

Weren't those same people at Apple before Jobs came back in the late 90's? I know some were if not all.

I still say 90% of apple's recent success is due to Jobs.

Absolutely not, all the current C-level staff was carefully brought together by Jobs in his, erm, "second coming".

Jobs is 100% responsible for creating the extremely successful Apple version 2. Wheter he's still crucial for this Apple's success, it's difficult to say.I'd say its ability to execute in the short and mid term should be completely not relying on Jobs anymore.Long term strategies, negotiating ability at the very top level, and that "sixth sense" for new products, who knows, we'll just need to sit and watch. I'd say that everything comes to an end eventually, even the infallibility of a top CEO instinct, so in the long term we would've had to sit and watch even if Jobs was in perfect health.

My standpoint is that Apple is Steve Jobs - as much as they don't want to be. Without him, they will still make money, but they'll eventually lose their way and become a company like any other.

Well, let's be positive - he'll come back once again. For how long, who knows, but he's a billionaire in his 50ies, chances of death are very small. He's not in good health, obviously - according to studies a liver transplant reduces life expectancy by 8 years on average. Chances there's another 10 years of Steve Jobs are therefore pretty high.

That said the stock is going to take a hit short term, and an even bigger one because people know it's going to take a hit. It's going to be very interesting tomorrow to see how the market will split between "fear of death of Steve Jobs" and "greedily expecting HUGE Q1 profits in the earnings call on the same day". I guess they planned it this way... evening out the tensions as well as they can. Still, it's going to take a dive. But it's uncertain how one could take advantage of it, given that everyone knows it. It might be a very large very short dip. Certainly going to be choppy waters out there.

I've just decided that I will be optimistic and speculate on a Steve Jobs comeback...

I guess it would be hugely ironic if Woz wound up outliving or at least enjoyed longer good-health than Jobs, given the different apparent dietary lifestyles. I'm reminded of the movie "Pirates of Silicon Valley" where Woz is eating shitty warmed up french fries at home in front of Jobs...

I'm a big fan of what Apple has done, and will follow this with great interest. Jobs and Apple have done more positive things for the average tech user (even those who are not their customers) than anybody else.

I was hoping that Jobs would do well for a long time, but nothing is forever. Here's to hoping that stupid license-plate free car is once again soon seen parking (perhaps inappropriately) in Apple's dual-purpose handicap/CEO parking space.